Research progress and prospect of pesticide droplet deposition characteristics

Abstract: Pesticide droplets can rebound, splash, and roll off the target surface during spraying, due mainly to insufficient wettability. The resulting environmental pollution has seriously threatened ecological stability and safety. However, the correlative mechanism of droplet deposition is still under exploration at present. It is necessary to explore the characteristics of effective droplet deposition for pest control. This study aims to review current researches on droplet deposition ranging from microdynamics of a single droplet and drift characteristics of the droplet group. The final deposition assessment and the bottleneck were also addressed, in order to clarify the research perspective of pesticide deposition. A single droplet model was essential to the impact mechanism of the droplet group because the pesticide droplets hit the target surface in the form of a single droplet during spraying. The previous reports on the deposition of the single droplet mainly contributed to the observation technologies, the influencing factors at the interface behavior of the single droplet, and the modeling of the single droplet hitting the target surface. However, the deposition behavior in the actual work depended mainly on the droplet distribution and canopy structure. There were two approaches to explore the deposition and drift characteristics in the spray field through the droplet group at present. One approach was that the observation and simulation were utilized to determine the movement of droplets in the spray field, thereby establishing the relationship between deposition behavior and amount. Another was to calculate the final deposition through actual experiments or simulation techniques, including the direct measurement of deposition on the surface of leaves, and the indirect measurement represented by the amount of drift in the air or on the ground. The research of droplet group was introduced to the distribution characteristics, deposition collection, and detection, as well as droplet group modeling. More importantly, a further combined modeling was necessary to accurately estimate the deposition behavior and the volume of deposited pesticides. The following suggestions can be drawn: 1) To establish the relationship between the single droplet and the droplet group modeling through the three-dimensional atomization field; 2) To estimate the amount of adhesion liquid after a single droplet hits the wall through image processing; 3) To explore the influence of wetted surfaces on deposition behavior; 4) To establish plant models in different growth periods. The finding can be widely expected to provide a strong reference for the research of pesticide deposition and pest control technologies.